Morphological techniques will be used to study major aspects of insulin action and provide structural correlates to biochemical data: 1. Use ferritin-insulin to characterize the insulin receptor in normal and abnormal conditions by electron microscopy. This will include development of a structural model to help explain various biochemical data concerning binding, including negative cooperativity. To document the fate of the insulin receptor during down regulation and to demonstrate any structural abnormalities in receptor distribution in insulin resistant states such as obesity and diabetes in both experimental animal models and man. 2. To demonstrate and characterize the insulin-sensitive plasma membrane ATPase by electron immunohistochemical methods and its relationship to the insulin receptor. This enzyme is directly stimulated by insulin and may play a vital role in the mechanism of insulin action. 3. To characterize the hormonal alterations of calcium content in various subcellular compartments by electron histochemical techniques and x-ray microprobe analysis. Biochemical studies in this laboratory have documented the ability of insulin treatment of fat cells to alter the calcium content and metabolism by various subcellular compartments as well as demonstrated an active insulin-sensitive calcium uptake system in the endoplasmic reticulum.